There exist some number of information processing apparatuses configured by connecting two types of units (devices) via a communication cable. A mass-production test for this type of information processing apparatus is implemented in the form of reattaching the communication cable to another two units undergoing the test next time from the two units with the test being completed, but a transmission error abruptly frequently occurs when the communication cable is repeatedly inserted and removed as the case may be.
The transmission error, however, occurs even if a trouble is caused on the unit side, and hence, it is the status quo to perform an operation of determining at first whether the transmission error is caused by the communication cable or on the unit side (an operation of troubleshooting the error portion distinctively).